I order mine online from Heritage Poutry and Livestock:
https://heritagelivestock.co.uk/product-category/animal-feeds/quail-feed/?v=79cba1185463. Their starter pack was good value and really helpful for a first-time quail keeper, though I see it's currently out of stock.
I'm in East Sussex. I have 10 ducks and a pair of Shetland geese and started this year with quail. I'm finding them hard to hatch: of my first batch of 12, 7 hatched, one died immediately and I found one (now fully-grown) dead in the cage yesterday morning. Of the second batch of 12, two died during hatching and 5 survived, but of them one died overnight and one had splayed feet that I couldn't correct and died after a week. So 4 adults and 3 chicks from two dozen mixed coturnix hatching eggs.